System and method for oxygenation of waste water

ABSTRACT

Oxygen is mixed with waste water at an early stage in a water treatment facility, to reduce odor caused by anaerobic reactions of sulfur. Waste water is withdrawn from a collection basin, by a pump connected to a suction pipe, and is mixed with oxygen from an external source. The mixture, having been saturated with oxygen, is then returned to the collection basin through a discharge pipe. The end of the discharge pipe is positioned at a higher vertical level than the end of the suction pipe, to prevent gas from entering the pump which would cause cavitation. Also, the end of the discharge pipe has a blind flange, such that the oxygen-enriched water exiting the discharge pipe flows in a direction which is non-parallel to the axis of the pipe. This arrangement provides better mixing of the oxygen with the water in the basin, and prevents the oxygen-enriched water from flowing too soon to the suction pipe. The invention substantially improves the efficiency and efficacy of waste water treatment, because it provides an economical way to oxygenate the waste water at an early stage in the treatment process.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to the field of waste watertreatment, and provides a system and method for oxygenating waste waterat an early stage of the waste water treatment process.

[0002] In a typical waste water treatment facility, waste water iscollected from various sources, including residential and/or industrialsources. The waste water from these sources is initially held in acollection basin, also known as a diversion box. The water is thenconveyed to one or more settling tanks, wherein debris in the water isallowed to settle. The water can then be filtered one or more times,aerated, and treated with chemicals such as ozone, chlorine, etc. Theremay be one or more further collection basins positioned before the firstfiltration stage.

[0003] Bacteria in the water attack organic material in the water,consuming oxygen in the process. But since the water reaching thecollection basin is delivered through underground conduits, the supplyof oxygen in the water is limited. If there is insufficient oxygenavailable to support the reactions which would naturally occur in thepresence of oxygen, anaerobic reactions take place instead. Suchreactions typically include the chemical combination of sulfur withhydrogen to produce hydrogen sulfide, a very odorous gas. Elimination offoul odors, and promoting biological oxidation reactions, are majorconcerns in the field of waste water treatment.

[0004] The known solution to the above-described problem is to oxygenatethe water. When the deficiency of dissolved oxygen is overcome, the odorproblem is greatly reduced or eliminated.

[0005] It has therefore been proposed, in the prior art, to provide asource of pure oxygen at high pressure, to dissolve this oxygen in asample of the waste water, and to return the oxygenated sample to thebasin being treated.

[0006] One prior art arrangement for performing the above steps is shownin FIG. 1. Oxygen From a supply (not shown) flows into conduit 1,through valve 3, and into mixing device 5. Waste water located incollection basin 7 is drawn out by pump 11, through suction pipe 9, andsent to the mixing device. The mixture of oxygen and waste water is thenintroduced into the collection basin through discharge pipe 13. Thedischarge pipe is connected to a plurality of nozzles 15 located at ornear the bottom of the collection basin.

[0007] The major problem with the method described above is that thenozzles easily become clogged with debris which is almost always presentin the waste water.

[0008] Another proposed solution of the prior art is shown in FIG. 2. Inthis embodiment, the nozzles have been eliminated. Instead, the ends ofdischarge pipe 21 and suction pipe 23 are displaced from the bottom ofthe basin. In the example given in the figure, these ends are positionedabout midway between the top and bottom of the basin. In this embodimentthere are two oxygen lines, one of which is used as a backup in theevent that the pump 27 becomes clogged or in the event that cavitationrenders the pump ineffective. Also in this embodiment, a screen (notshown) is used at the inlet to suction pipe 23, to prevent debris in thewater from interfering with the operation of pump 27.

[0009] The system described above is still not practical. Its majorproblem is that it causes cavitation in the pump. As the screen becomesclogged, the pump has less and less to pull, resulting in reducedsuction in the line. Changes in pressure in the line may cause oxygen tocome out of solution, and if this occurs, the pump will tend to pullboth gas and water out of the basin. The presence of gas in the linecauses damage to the pump.

[0010] The present invention provides a system and method which allowsthe oxygenation of waste water in a collection basin, but whichnevertheless does not suffer from the disadvantages of the prior artdescribed above.

SUMMARY OF THE INVENTION

[0011] The present invention comprises a system which connects a sourceof pressurized oxygen to a mixing device. A pump draws some of the wastewater out of a collection basin, and directs this water to the mixingdevice, where the water and oxygen are mixed so that the oxygen isdissolved in the water. This oxygen-enriched water produced in themixing device is conveyed to a discharge pipe, the end of which sitswithin the waste water in the basin. A suction pipe, connected to thepump, withdraws a portion of the contents of the basin. The ends of thedischarge pipe and the suction pipe are at different vertical levels. Inthe preferred embodiment, the end of the discharge pipe is located abovethe end of the suction pipe. In operation, water is continuouslywithdrawn from the basin, while oxygen-enriched water is continuouslyinjected into the basin.

[0012] The end of the discharge pipe preferably includes a blind flange,which tends to prevent returned waste water from flowing directly out ofthe discharge pipe. Instead, the oxygen-water mixture is directed out ofthe discharge pipe, through holes in its side wall, in a direction whichis non-parallel to the longitudinal axis of the pipe. This arrangementassures that the mixture will not directly enter the suction pipe, butwill instead become evenly dispersed through the basin. Thus, thesuction pipe does not “short-circuit” the discharge pipe.

[0013] The invention therefore also includes the method of oxygenatingthe contents of a waste water collection basin by mixing some of thewaste water with oxygen, such that the oxygen becomes dissolved in thewater, and introducing the oxygen-enriched water into the basin at avertical level different from that at which water in the basin isremoved. The introducing step is performed by introducing the mixture ina direction which is generally perpendicular, or at least non-parallel,to the flow of fluid in the discharge pipe.

[0014] The present invention virtually eliminates the cavitation problemassociated with systems of the prior art, making it feasible tooxygenate waste water at an early stage of its processing.

[0015] The present invention therefore has the primary object ofproviding a system and method for oxygenation of waste water.

[0016] The invention has the further object of preventing cavitation ina pump used to draw waste water from a collection basin, for use in anoxygenation process.

[0017] The invention has the further object of reducing or eliminatingfoul odors in a collection basin in a waste water treatment facility.

[0018] The invention has the further object of oxygenating waste waterat a relatively early stage in a waste water treatment plant.

[0019] The invention has the further object of improving the efficiencyand effectiveness of waste water treatment.

[0020] The reader skilled in the art will recognize other objects andadvantages of the present invention, from a reading of the followingbrief description of the drawings, the detailed description of theinvention, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 provides a schematic diagram of a system of the prior art,for oxygenating waste water in a collection basin.

[0022]FIG. 2 provides a schematic diagram of another system of the priorart, for oxygenating waste water.

[0023]FIG. 3 provides a schematic diagram of the system of the presentinvention.

[0024]FIG. 4 provides a fragmentary elevational view of the end of thedischarge pipe used in the present invention.

[0025]FIG. 5 provides a block diagram of a typical waste water treatmentfacility using the method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0026]FIG. 3 provides a schematic diagram of the system of the presentinvention. Oxygen from a supply (not shown) flows into the systemthrough conduit 31. The oxygen is preferably at a high pressure,typically 150 psig. The oxygen flows to sparging or mixing unit 33through conduit 35, which includes manual blocking valve 37, pressureregulator 39, flow control valve 41, solenoid valve 43, and check valve45. The solenoid valve is intended to close in the event of anemergency. The contents of the mixing unit pass through blocking valve47, and then through discharge pipe 49 which terminates in collectionbasin 51.

[0027] Suction pipe 53 also has an end terminating in the collectionbasin, and is connected to pump 55. The output of the pump passesthrough check valve 57, blocking valve 59, and then to mixing unit 33.The blocking valves allow portions of the system to be isolated formaintenance.

[0028] The pump is preferably a self-priming pump. In one embodiment,the pump may have a capacity of about 600 gallons per minute. Pumpshaving a capacity greater or less than 600 gpm can be used, depending onthe size of the system. The invention is not limited to a specificcapacity.

[0029] An oxygen bypass line 61 provides an alternate path for oxygen inthe event of cavitation in the pump, or if the pump becomes inoperativefor some other reason.

[0030] The end 63 of the discharge pipe is displaced vertically relativeto the end 65 of the suction pipe. In the preferred embodiment, the endof the discharge pipe is positioned above the end of the suction pipe.This vertical displacement is represented by reference symbol “a” inFIG. 3. In one example, the value of “a” may be about two feet. Thelatter dimension is given only as an example, and is not intended tolimit the invention. The optimum height difference between the two pipesmay be affected by other factors, such as the flow rate of the water,the amount of oxygen dissolved, and the size of the basin.

[0031] The discharge pipe and the suction pipe should be spacedsufficiently close that the oxygen remains in the main flow stream, butsufficiently far apart that the oxygen does not “short-circuit”, i.e.that it does not enter the suction pipe before having spent any time inthe basin. It is important that the oxygen remain in flowing water; theoxygen will not serve the desired purpose in stagnant water. Theresidence time of the oxygen in the water is short, and if the oxygen isnot used immediately, it will not be effective in supporting the desiredchemical reactions.

[0032] In operation, water from the basin is withdrawn continuouslythrough the suction pipe, and the oxygen-enriched water from the mixingunit is continuously conveyed into the basin through the discharge pipe.Due to the action of the pump, these steps are performed simultaneously.

[0033] Positioning the ends of the discharge pipe and the suction pipeat different heights tends to prevent gas from entering the suctionpipe, thus preventing cavitation in the pump. The oxygen mixed with thewater is dissolved in the water before it reaches the suction pipe, andthus there is no gas to cause cavitation. Moreover, the use of watercontaining dissolved oxygen provides the conditions necessary to reduceor eliminate foul odors in the water.

[0034]FIG. 4 shows the preferred structure of the end of the dischargepipe. The discharge pipe includes cylindrical body 67 having holes 69formed in the side wall of the body. The pipe also includes blind flange71 which is offset from the end of the pipe. That is, an opening isformed between the end of the discharge pipe and the blind flange. Thus,the blind flange inhibits the flow of fluid directly out of the end ofthe discharge pipe. Some of the fluid in the discharge pipe will flowout through the holes 69, and some of the fluid will be diverted by theblind flange, and will flow out through the opening between the end ofthe discharge pipe and the blind flange. In either case, fluid exits thedischarge pipe in a direction indicated by arrow 73, which is generallyperpendicular, or at least non-parallel, to the longitudinal axis of thepipe, which is the direction of flow of fluid in the pipe. Thisarrangement tends to prevent gas from entering the suction pipe beforeit is further mixed with the waste water.

[0035] The use of the discharge pipe having the structure shown in FIG.4 further helps to mix the oxygen more thoroughly with the waste water,as the waste water and oxygen mixture is directed laterally through thecollection basin, and not directly to the area of the suction pipe.Also, the fact that the ends of the discharge pipe and suction pipe arevertically displaced from each other further reduces the“short-circuiting” effect wherein water tends to flow out of thedischarge pipe and directly into the suction pipe. Proper treatment ofthe waste water requires that the oxygen be mixed uniformly through thebasin. The present invention accomplishes this aim in a practical andefficient manner.

[0036] In the prior art system of FIG. 2, a screen was used on the inletto the suction pipe to prevent debris from reaching the pump. Experiencewith the arrangement of FIG. 2 has shown that the screen itself becomesquickly clogged with debris. In the present invention, there is no suchscreen. One can select the size of the pump so as to handle debris of agiven size. The risk to the pump comes from cavitation, but, asexplained above, the present invention reduces or eliminates this risk.

[0037]FIG. 5 provides a block diagram of a typical waste water treatmentfacility, as modified according to the present invention. This diagramshows the stages of the system, and the steps of the method, fortreating the waste water.

[0038] Waste water enters through conduit 100, and flows into primarydiversion box (or basin) 101. Debris settles out of the water in primarysettling tank 102. Sludge from this tank exits through line 112. Theremay be a plurality of primary settling tanks, in which case such tankswould be connected in parallel. The water then flows into a first stagetrickling filter diversion box 103. The water is then filtered intrickling filter 104, which could also comprise a plurality of filtersconnected in parallel. The filtered water passes to trickling filterconversion box 105, and into tertiary settling tank 106. As before, tank106 could be replaced by a plurality of tanks connected in parallel.

[0039] Next, the water flows to tertiary aeration tank 107, and to finaldiversion box 108. Sludge from diversion box 108 is recycled, throughline 111, to the primary settling tank 102. In intermediate diversionbox 109, the water is treated with chlorine, and the treated water flowsinto intermediate tank 110 (which could comprise more than one tankconnected in parallel) and out of the system through line 113.

[0040]FIG. 5 also illustrates, schematically, the injection of theoxygen-enriched water, through line 115, and the withdrawal of waterfrom the basin, through line 117, as described earlier.

[0041] In the embodiment shown, oxygen is mixed with the water indiversion box (or collection basin) 101, which comprises the first majorstep of the water treatment process. Oxygen could also be injected atlater points in the process.

[0042] The present invention is believed to be the first practicalsystem for oxygenation of waste water in a collection basin. In theprior art, it has been known to oxygenate waste water, but only at laterstages in the water treatment process, such as in aeration basinspositioned considerably downstream of the waste water intake. Byeffectively oxygenating waste water in a collection basin, i.e. at ornear the point where the waste water first enters the system, and in anycase before the first significant filtration or treatment step, onegreatly improves the efficiency of the water treatment process.

[0043] The invention can be modified in various ways. The specificarrangement of blocking valves and pressure regulators can be variedaccording to the needs of the user. The specific shape of the collectionbasin may vary. The invention is not limited by the particular structureof the mixing unit or of the pump. These and other similar modificationswill be apparent to the reader skilled in the art, and should beconsidered within the spirit and scope of the following claims.

What is claimed is:
 1. A system for dissolving oxygen in a waste watercollection basin, comprising: a) a source of oxygen, the oxygen sourcebeing connected to a discharge pipe having an end located in thecollection basin, b) a suction pipe having an end located in thecollection basin, and c) a pump connected to the suction pipe and to amixing unit which is connected to the oxygen source, wherein the end ofthe discharge pipe is positioned above a level of the end of the suctionpipe.
 2. The system of claim 1 , wherein the discharge pipe has a sidewall, wherein the discharge pipe has a plurality of holes disposed inthe side wall, and wherein the discharge pipe includes a blind flangeconnected to the end of the discharge pipe.
 3. A system for dissolvingoxygen in a waste water collection basin, comprising: a) a source ofoxygen, the oxygen source being connected to a discharge pipe having anend located in the collection basin, b) a suction pipe having an endlocated in the collection basin, and c) a pump connected to the suctionpipe and to a mixing unit which is connected to the oxygen source,wherein the discharge pipe has a side wall, wherein the discharge pipehas a plurality of holes disposed in the side wall, and wherein thedischarge pipe includes a blind flange connected to the end of thedischarge pipe.
 4. The system of claim 3 , wherein the end of thedischarge pipe is positioned, within the collection basin, above a levelof the end of the suction pipe.
 5. The system of claim 4 , wherein theend of the discharge pipe is positioned at least two feet above thelevel of the end of the suction pipe.
 6. A system for oxygenation ofwaste water in a collection basin, comprising: a) means for providingpressurized oxygen, b) means for withdrawing waste water from thecollection basin, c) means for mixing oxygen from the oxygen providingmeans with waste water from the withdrawing means to produceoxygen-enriched water, and d) means for conveying said oxygen-enrichedwater to the collection basin and for discharging said oxygen-enrichedwater into the collection basin, wherein the discharging means ispositioned at a vertical level which is different from a vertical levelof the withdrawing means.
 7. The system of claim 6 , wherein thedischarging means includes a conduit having a longitudinal axis, andwherein the conduit includes means for directing fluid flow out of theconduit in a direction which is non-parallel to said longitudinal axis.8. A system for oxygenation of waste water in a collection basin,comprising: a) means for providing pressurized oxygen, b) means forwithdrawing waste water from the collection basin, c) means for mixingoxygen from the oxygen providing means with waste water from thewithdrawing means to produce oxygen-enriched water, and d) means forconveying said oxygen-enriched water to the collection basin and fordischarging said oxygen-enriched water into the collection basin,wherein the discharging means includes a conduit having a longitudinalaxis, and wherein the conduit includes means for directing fluid flowout of the conduit in a direction which is non-parallel to saidlongitudinal axis.
 9. A method of oxygenating waste water in acollection basin, the method comprising: a) withdrawing waste water fromthe collection basin, b) mixing the waste water withdrawn in step (a)with oxygen to form oxygen-enriched water, and c) injecting saidoxygen-enriched water into the collection basin, wherein the injectingstep and the withdrawing step are performed simultaneously at differentvertical levels within the collection basin.
 10. The method of claim 9 ,wherein the injecting step is performed at a higher vertical level thanthe withdrawing step.
 11. The method of claim 9 , wherein the injectingstep comprises delivering the oxygen-enriched water to the collectionbasin through a conduit having a longitudinal axis, and directing theoxygen-enriched water out of the conduit in a direction which isnon-parallel to said longitudinal axis.
 12. The method of claim 10 ,wherein the injecting step comprises delivering the oxygen-enrichedwater to the collection basin through a conduit having a longitudinalaxis, and directing the oxygen-enriched water out of the conduit in adirection which is non-parallel to said longitudinal axis.
 13. A methodof oxygenating waste water in a collection basin, the method comprising:a) withdrawing waste water from the collection basin, b) mixing thewaste water withdrawn in step (a) with oxygen to form oxygen-enrichedwater, and c) injecting said oxygen-enriched water into the collectionbasin, wherein the injecting step comprises delivering theoxygen-enriched water to the collection basin through a conduit having alongitudinal axis, and directing the oxygen-enriched water out of theconduit in a direction which is non-parallel to said longitudinal axis.14. In a waste water treatment system, the system having a plurality ofwater treatment stages, the water treatment stages being preceded by atleast one collection stage, the improvement comprising a source ofoxygen connected to said collection stage, wherein oxygen is mixed withwaste water in the collection stage before being treated in the system.15. The improvement of claim 14 , further comprising a suction pipehaving an end located in the collection stage, and a pump connected tothe suction pipe and to a mixing unit which is connected to the oxygensource, wherein the end of the discharge pipe is positioned above alevel of the end of the suction pipe.
 16. The improvement of claim 14 ,wherein the source of oxygen enters the collection stage through adischarge pipe, and wherein the discharge pipe has a side wall, whereinthe discharge pipe has a plurality of holes disposed in the side wall,and wherein the discharge pipe includes a blind flange connected to theend of the discharge pipe.
 17. The improvement of claim 15 , wherein thesource of oxygen enters the collection stage through a discharge pipe,and wherein the discharge pipe has a side wall, wherein the dischargepipe has a plurality of holes disposed in the side wall, and wherein thedischarge pipe includes a blind flange connected to the end of thedischarge pipe.
 18. In a method for treating waste water, the methodincluding treating the water in a plurality of water treatment steps,the water treatment steps being preceded by at least one waste watercollection step, the improvement comprising mixing oxygen with the wastewater, during the collection step, before treating the waste water. 19.The improvement of claim 18 , wherein the mixing step compriseswithdrawing waste water from a collection basin, mixing the withdrawnwaste water with oxygen to form oxygen-enriched water, and injecting theoxygen-enriched water into the collection basin, wherein the withdrawingand injecting steps are performed at different vertical levels withinthe collection basin.
 20. The improvement of claim 19 , wherein theinjecting step is performed by passing the oxygen-enriched water througha discharge pipe having a longitudinal axis, and directing theoxygen-enriched water out of the discharge pipe in a direction which isnon-parallel to said longitudinal axis.